Conventional microelectronic devices are manufactured for specific performance characteristics required for use in a wide range of electronic equipment. A microelectronic bare die, for example, includes an integrated circuit and a plurality of bond-pads and/or redistribution layer (RDL) pads electrically coupled to the integrated circuit. The bond-pads can be arranged in an array, and a plurality of solder balls can be attached to corresponding bond-pads to construct a “ball-grid array.” Conventional bare dies with ball-grid arrays generally have solder balls arranged, for example, in 6×9, 6×10, 6×12, 6×15, 6×16, 8×12, 8×14, or 8×16 patterns, but other patterns are also used. Many bare dies with different circuitry can have the same ball-grid array but different outer profiles.
Bare dies are generally tested in a post-production batch process to determine which dies are defective. In one conventional test process, bare dies are placed in corresponding test sockets of a test tray and electrical signals are applied to the dies in a controlled environment. FIG. 1, for example, is a schematic side cross-sectional view of a portion of a conventional testing system 10 including a test bed 20 carrying a bare die 30. The test bed 20 includes a test socket 22 having lead-in surfaces 24 and side surfaces 26 that define a recess 28 for receiving the die 30. A tester interface 40 including a plurality of test contacts 42 is positioned below the test bed 20 with the test contacts 42 positioned to contact corresponding solder balls 32 on the die 30. A pusher assembly 50 (shown schematically) is positioned above the die 30 and configured receive a force from an actuator 60 and move the die 30 toward the tester interface 40 (as shown by the arrows A) so that the test contacts 42 can apply electrical signals to the die for testing. Although only a single test socket 22, die 30, and pusher assembly 50 are shown in FIG. 1, it will be appreciated that the system 10 can include a number of test sockets 22 and pusher assemblies 50 for testing a number of dies either individually or in a batch process.
The pusher assembly 50 is configured to exert a desired force on the die 30 so that the solder balls 32 contact corresponding test contacts 42 with a desired contact force and without damaging the solder balls. Precise and repeatable positioning of each die 30 with respect to the test contacts 42 is essential for accurate and efficient testing of the dies. Examples of conventional pusher assemblies include the M6541-, M6741-, and M6542-series pusher assemblies commercially available from Advantest Corporation of Tokyo, Japan.
One problem with conventional pusher assemblies, such as the pusher assembly 50, is that it is difficult to perform testing for runs of dies with different profiles. In many conventional testing systems, for example, the pusher assemblies are specifically configured to be used throughout a testing run for dies having the same outer profile and/or ball grid array. However, to test dies with different profiles or ball grid arrays using the same test bed requires reconfiguring the pusher assembly to accommodate the different outer profile and/or ball grid of the new dies to be tested. The pusher assembly is generally reconfigured by manually removing all or a substantial portion of the pusher assembly from the system and attaching a different pusher assembly specifically sized and configured for the outer profile of the new dies to be tested. In a typical large scale manufacturing process for microfeature devices (such as bare dies), reconfiguring the pusher assemblies to test dies having a different outer profile typically involves reconfiguring a large number of pusher assemblies. This process is accordingly extremely labor-intensive, time-consuming, and expensive because it not only requires a large inventory of pusher assemblies having different configurations and many hours of skilled labor, but it also results in costly downtime for the testing systems.
Another problem with testing systems including conventional pusher assemblies is that it can be difficult to keep the die and other system components at a desired temperature throughout the testing process. The lack of a heat transfer device on conventional pusher assemblies can create a significant problem with overheating during testing. Further, the addition of such a heat transfer unit to many conventional pusher assemblies would interfere with the operation and placement of the pusher assembly within the testing system. Accordingly, there is a need for an improved pusher assembly for use in microfeature device testing systems.